Light-responsive biomaterials are an emerging class of materials used for developing noninvasive, noncontact, precise, and controllable biomedical devices. Long-wavelength near-infrared (NIR) radiation is an attractive light source for in situ gelation due to its higher penetration depth and minimum side effects. The conventional approach to obtain crosslinked biomaterials relies heavily on the use of a photoinitiator by generating reactive species when exposed to short-wavelength radiation, which is detrimental to surrounding cells and tissue. Here, a new class of NIR-triggered in situ gelation system based on defect-rich 2D molybdenum disulfide (MoS2 ) nanoassemblies and thiol-functionalized thermoresponsive polymer in the absence of a photoinitiator is introduced. Exposure to NIR radiation activates the dynamic polymer-nanomaterials interactions by leveraging the photothermal characteristics of MoS2 and intrinsic phase transition ability of the thermoresponsive polymer. Specifically, upon NIR exposure, MoS2 acts as a crosslink epicenter by connecting with multiple polymeric chains via defect-driven click chemistry. As a proof-of-concept, the utility of NIR-triggered in situ gelation is demonstrated in vitro and in vivo. Additionally, the crosslinked gel exhibits the potential for NIR light-responsive release of encapsulated therapeutics. https://www.selleckchem.com/products/og-l002.html These light-responsive biomaterials have strong potential for a range of biomedical applications, including artificial muscle, smart actuators, 3D/4D printing, regenerative medicine, and therapeutic delivery.Few-layer van der Waals (vdW) materials have been extensively investigated in terms of their exceptional electronic, optoelectronic, optical, and thermal properties. Simultaneously, a complete evaluation of their mechanical properties remains an undeniable challenge due to the small lateral sizes of samples and the limitations of experimental tools. In particular, there is no systematic experimental study providing unambiguous evidence on whether the reduction of vdW thickness down to few layers results in elastic softening or stiffening with respect to the bulk. In this work, micro-Brillouin light scattering is employed to investigate the anisotropic elastic properties of single-crystal free-standing 2H-MoSe2 as a function of thickness, down to three molecular layers. The so-called elastic size effect, that is, significant and systematic elastic softening of the material with decreasing numbers of layers is reported. In addition, this approach allows for a complete mechanical examination of few-layer membranes, that is, their elasticity, residual stress, and thickness, which can be easily extended to other vdW materials. The presented results shed new light on the ongoing debate on the elastic size-effect and are relevant for performance and durability of implementation of vdW materials as resonators, optoelectronic, and thermoelectric devices.Magnetic miniature robots (MMRs) are small-scale, untethered actuators which can be controlled by magnetic fields. As these actuators can non-invasively access highly confined and enclosed spaces; they have great potential to revolutionize numerous applications in robotics, materials science, and biomedicine. While the creation of MMRs with six-degrees-of-freedom (six-DOF) represents a major advancement for this class of actuators, these robots are not widely adopted due to two critical limitations i) under precise orientation control, these MMRs have slow sixth-DOF angular velocities (4 degree s-1 ) and it is difficult to apply desired magnetic forces on them; ii) such MMRs cannot perform soft-bodied functionalities. Here a fabrication method that can magnetize optimal MMRs to produce 51-297-fold larger sixth-DOF torque than existing small-scale, magnetic actuators is introduced. A universal actuation method that is applicable for rigid and soft MMRs with six-DOF is also proposed. Under precise orientation control, the optimal MMRs can execute full six-DOF motions reliably and achieve sixth-DOF angular velocities of 173 degree s-1 . The soft MMRs can display unprecedented functionalities; the six-DOF jellyfish-like robot can swim across barriers impassable by existing similar devices and the six-DOF gripper is 20-folds quicker than its five-DOF predecessor in completing a complicated, small-scale assembly.Understanding and controlling the energy level alignment at interfaces with metal halide perovskites (MHPs) is essential for realizing the full potential of these materials for use in optoelectronic devices. To date, however, the basic electronic properties of MHPs are still under debate. Particularly, reported Fermi level positions in the energy gap vary from indicating strong n- to strong p-type character for nominally identical materials, raising serious questions about intrinsic and extrinsic defects as dopants. In this work, photoemission experiments demonstrate that thin films of the prototypical methylammonium lead triiodide (MAPbI3 ) behave like an intrinsic semiconductor in the absence of oxygen. Oxygen is then shown to be able to reversibly diffuse into and out of the MAPbI3 bulk, requiring rather long saturation timescales of ?1 h (in ambient air) and over 10 h (out ultrahigh vacuum), for few 100 nm thick films. Oxygen in the bulk leads to pronounced p-doping, positioning the Fermi level universally ?0.55 eV above the valence band maximum. The key doping mechanism is suggested to be molecular oxygen substitution of iodine vacancies, supported by density functional theory calculations. This insight rationalizes previous and future electronic property studies of MHPs and calls for meticulous oxygen exposure protocols.Current synthetic elastomers suffer from the well-known trade-off between toughness and stiffness. By a combination of multiscale experiments and atomistic simulations, a transparent unfilled elastomer with simultaneously enhanced toughness and stiffness is demonstrated. The designed elastomer comprises homogeneous networks with ultrastrong, reversible, and sacrificial octuple hydrogen bonding (HB), which evenly distribute the stress to each polymer chain during loading, thus enhancing stretchability and delaying fracture. Strong HBs and corresponding nanodomains enhance the stiffness by restricting the network mobility, and at the same time improve the toughness by dissipating energy during the transformation between different configurations. In addition, the stiffness mismatch between the hard HB domain and the soft poly(dimethylsiloxane)-rich phase promotes crack deflection and branching, which can further dissipate energy and alleviate local stress. These cooperative mechanisms endow the elastomer with both high fracture toughness (17016 J m-2 ) and high Young's modulus (14.